Contact arrangement for a vacuum interrupter

ABSTRACT

In a vacuum interrupter for circuit breakers, the aim is to reduce the contact pressure force. The contacts of the vacuum interrupter are configured for this purpose such that there is arranged inside an outer contact region, serving the purpose of arc quenching, an inner contact region which includes a plurality of resilient contact tongues arranged next to one another on a divided circle.

This application is the national phase under 35 U.S.C. §371 of PCTInternational Application No. PCT/DE00/02443 which has an Internationalfiling date of Jul. 20, 2000, which designated the United States ofAmerica, the entire contents of which are hereby incorporated byreference.

FIELD OF THE INVENTION

The invention generally relates to the field of electric components, andis preferably to be applied in designing the configuration of vacuuminterrupters. More preferably, it relates to vacuum interrupters inwhich at least one of the two contacts has an inner contact region whichprojects axially over an outer contact region serving the purpose of arcquenching.

BACKGROUND OF THE INVENTION

Vacuum interrupters with contact arrangements of the type are known. Inthis case, the two contacts, of which, generally speaking, only one canbe moved axially relative to the other, are fitted with circular orslightly conical contact surfaces which face one another. Contacts whichare constructed as what are termed “vane/blade electrodes” or “spiralcontacts” have an inner contact region provided for switching operatingcurrents, and an outer contact region, which surrounds the inner contactregion concentrically, is provided for interrupting short-circuitcurrents and serves as running surface for a rotating arc. In this case,the inner contact region projects over the outer contact region by acertain, not very large amount (U.S. Pat. Nos. 3,158,719 A, 3,809,836A).

Vacuum interrupters are also known in which the contact region providedfor switching operating currents is identical with the contact regionprovided for interrupting the short-circuit currents. These contacts areof cup-shaped construction, the wall of the cup and, if appropriate,also the contact ring mounted on the top edge being provided with aplurality of slits which run obliquely relative to the longitudinal axisof the contact arrangement. The contact surface can be subdivided into aplurality of contact subsurfaces by means of these slits (DE 23 21 753A1, DE 29 12 823 A1).

In order to be able to separate welded contact regions more easily fromone another in the case of vacuum interrupters, it is known to give eachcontact a relatively large number of contact surfaces and to hold theseelastically on a main contact body. A tubular main contact body can beprovided for this purpose with radially inwardly projecting support armsfor the contact surfaces (U.S. Pat. No. 3,869,589 A).

Furthermore, for air-switching circuit breakers in the low-voltage fieldit is known per se to split up the movable contact into a plurality ofcontact fingers arranged parallel to one another, for the purpose ofreducing the contact pressure force (U.S. Pat. No. 5,210,385 A).

In vacuum interrupters for circuit breakers, in particular for circuitbreakers in the low-voltage field (for example U.S. Pat. No. 5,661,281),the high currents give rise to high forces on the contacts which tend toraise the contacts off one another. These current forces must becompensated by means of suitable measures so that the contacts do notlift off with the risk of them becoming welded to one another. In thecase of switches fitted with vacuum interrupters, this problem has beensolved so far by making use, in addition to a permanently applied staticcontact pressure force, of an additional current loop with the aid ofwhich high dynamic magnetic field forces which act to strengthen thecontact force are produced in the short term, that is to sayparticularly during the occurrence of short circuit currents. There isno need thereby for mechanical application of the entire contactpressure force, which is required only in the short term. Because of therelatively high costs of such current loops, the contact force to bemechanically applied in a permanent fashion continues, however, to berelatively large and can be several kN per switching pole, particularlyin the case of high currents of more than 50 kA. This requires acorrespondingly high mechanical outlay in the switching device.

SUMMARY OF THE INVENTION

Starting from a contact arrangement having the features of the preambleof patent claim 1, it is an object of the invention to construct thecontact arrangement such that the mechanical contact point isdistributed over a plurality of separate individual contacts with adefined spring constant, and that an arc can nevertheless rotate.

In order to achieve this object, for example, it is provided accordingto the invention that the inner contact region including a plurality ofcontact subregions arranged next to one another on a divided circle,each contact subregion being formed by the free end of a resilientcontact tongue inclined relative to the axis of the contact arrangement.

Such a configuration of the contact arrangement permits the contactregion provided for switching operating currents to be broken down intoa larger number of, for example, three to ten subregions and for thesesubregions to be constructed as resilient contact tongues opposite whichthere is a mating contact piece in each case, and to decouple thecontact tongues so far from one another mechanically by appropriatedimensioning of the spring constant that in the closed state of thecontact arrangement all the subregions are subjected to a contactpressure force of the same magnitude. The resilient contact tongues canbe arranged in this case such that upon opening and closing of thecontact system a frictional movement is avoided, and thus so is abrasionin the form of metallic chips.

In order to have sufficient space to configure the dimensioning of thespring constants of the contact tongues, the contact tongues can beproduced from a flat, conical shell by multiply slitting the shell wallin an axial fashion. In this case, the spring constant can be varied, inparticular, by the thickness of the shell wall and the number of theslits and/or the width of the contact tongues. Similar relationships areobtained when the contact tongues are produced from a flat, hollowconical frustum by multiply slitting the conical lateral surface in anaxial fashion.

In a way resembling the configuration of the slit contact carrier ofwhat are termed cup-shaped contacts, the contact tongues can also beproduced from a tube length by providing the wall thereof with aplurality of obliquely running slits.

The design configuration described for the contact tongues can beapplied both in the case of spiral contacts and in the case ofcup-shaped contacts. The body used for the contact tongues can include,in this case of dispersion-hardened copper, a specific copper alloy or acopper/chromium material with a small proportion of chromium. It isfabricated separately and arranged in the middle of the respectivecontact in an appropriate cutout and soldered to the remaining contactbody.

BRIEF DESCRIPTION OF THE DRAWINGS

A plurality of exemplary embodiments of contact arrangements constructedin accordance with the invention are illustrated in FIGS. 1 to 7. In thedrawings:

FIG. 1 shows a first exemplary embodiment of a contact arrangement inwhich the inner contact region is formed by a shell-shaped contact body,

FIG. 2 shows a top view of a contact arrangement in accordance with FIG.1,

FIG. 3 shows a second exemplary embodiment of a contact arrangement,with an inner contact region constructed as a hollow conical frustum,

FIG. 4 shows a third exemplary embodiment, with an inner contact regionconstructed as a slit tube length,

FIG. 5 shows a schematic illustration of the inner contact region inaccordance with FIG. 4, in a side view, and

FIGS. 6 and 7 show a fourth exemplary embodiment, with an inner contactregion likewise constructed as a slit tube length.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The contact arrangement in accordance with FIG. 1 includes an uppercontact 1 and a lower contact 2, which are arranged axially relative toone another along an axis A with mutually facing contact surfaces. Inthis arrangement, one contact can be moved axially—in a way not shown inmore detail, but known. Each of the two contacts 1 and 2 is providedwith a current supply lead 3 and 4, respectively.

In accordance with FIG. 2, each contact is constructed as what is termeda “spiral contact” in accordance with European patent 0 332 513 B1, eachslit 5 including two sections, of which the first section runs parallelto a tangent, applied to the circumference of a circular cutout 6, andof which the second section includes a bore which, in the region of theinner end of the first section, penetrates the contact surface betweenthe first section and the circular cutout 6. The region of the contactwhich is situated outside the cutout 6 forms an outer contact region 7which is provided for interrupting short-circuit currents and serves asrunning surface for a rotating arc.

The cutout 6 is designed so deeply that it can accommodate an additionalcontact body 8, which forms an inner contact region 9. This innercontact region 9, which is provided for switching operating currents,projects axially over the outer contact region 7, arrangedconcentrically with the inner contact region, by a certain length a,which is 2 mm, for example.

In accordance with FIGS. 1 and 2, the contact body 8 has the shape of aflat, conical shell whose shell wall is multiply slit in the axialdirection. A plurality of contact subregions 10 are formed by this slitarrangement 12. The bottom of the shell-shaped contact body 8, which issoldered to the contact piece 1 or 2, is not slit, and so the slitarrangement forms a plurality of resilient contact tongues 11 which areinclined relative to the axis A of the contact arrangement and whosefree end forms a contact subregion 10 in each case.

In the case of a contact arrangement in accordance with FIG. 3, thecontact body 13 forming the inner contact region is constructed as aflat, hollow conical frustum whose lateral surface is multiply slit inan axial fashion. This slit arrangement does not go as far as the baseof the conical frustum, so as to be able to solder the contact body as awhole to the respective contact piece.

In the exemplary embodiment in accordance with FIG. 4, use is made inthe cutout 6 of the contacts 1 and 2 as contact body for the innercontact region of a hollow cylinder in the form of a tube length 14which is provided, in accordance with FIG. 5, with slits 15 runningobliquely to the axis of the contact arrangement, as a result of whichresilient contact tongues 16 are formed. Additionally arranged on theupper contact 1 inside the tube length 14 is a contact piece 17 whichforms a mechanical support in the closed state of the contacts 1 and 2.In the case of operating currents, this contact piece also conducts thecurrent, it being possible to achieve the lowest contact resistances asa result. In the case of short-circuit currents, as the additionalcontact piece 17 starts to lift off, that is to say when there is aslight rise in the contact resistance, the resilient contact regions ofthe contact body resembling a tube length take over the conducting ofcurrent and thus prevent complete lifting off and welding of the contactsystem.

The exemplary embodiment in accordance with FIGS. 6 and 7 shows acup-shaped contact 18 whose slit wall is covered at the cup edge with anannular contact disk 19, this contact disk forming the outer contactregion of the contact. Arranged inside the cup-shaped contact is acontact body 20 which is of similar construction to the contact body 14in accordance with FIGS. 4 and 5, and includes a tube length whose wallis provided with a plurality of obliquely running slits 21. The contactbody 20, which forms the inner contact region of the cup-shaped contact18, projects through the contact disk 19 axially by the length b, whichis 2 mm, for example.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. A contact arrangement for a vacuum interrupter,comprising: at least two contacts, axially movable relative to oneanother and including mutually facing contact surfaces, wherein eachcontact includes an inner contact region, provided for switchingoperating currents, and an outer contact region, which surrounds theinner contact region concentrically and which is provided forinterrupting short-circuit currents and which serves as running surfacefor a rotating arc, and wherein the inner contact region projectsaxially over the outer contact region and includes a plurality ofcontact subregions arranged next to one another on a divided circle,each contact subregion being formed by a free end of a resilient contacttongue inclined relative to an axis of the contact arrangement.
 2. Thecontact arrangement as claimed in claim 1, wherein the inner contactregion includes a flat, conical shell whose shell wall is multiply slitin an axial fashion.
 3. The contact arrangement as claimed in claim 1,wherein the inner contact region includes a flat, hollow conical frustumwhose lateral surface is multiply slit in an axial fashion.
 4. Thecontact arrangement as claimed in claim 1, wherein the inner contactregion includes a tube length whose wall is provided with a plurality ofobliquely running slits.
 5. The contact arrangement as claimed in claim1, wherein the outer contact region includes the arms of a spiralcontact.
 6. The contact arrangement as claimed in claim 1, wherein theouter contact region includes the contact surface of a cup-shapedcontact.
 7. The contact arrangement as claimed in claim 2, wherein theouter contact region includes the arms of a spiral contact.
 8. Thecontact arrangement as claimed in claim 3, wherein the outer contactregion includes the arms of a spiral contact.
 9. The contact arrangementas claimed in claim 4, wherein the outer contact region includes thearms of a spiral contact.
 10. The contact arrangement as claimed inclaim 2, wherein the outer contact region includes the contact surfaceof a cup-shaped contact.
 11. The contact arrangement as claimed in claim3, wherein the outer contact region includes the contact surface of acup-shaped contact.
 12. The contact arrangement as claimed in claim 4,wherein the outer contact region includes the contact surface of acup-shaped contact.
 13. A vacuum interrupter including the contactarrangement of claim
 1. 14. A vacuum interrupter including the contactarrangement of claim
 2. 15. A vacuum interrupter including the contactarrangement of claim
 3. 16. A vacuum interrupter including the contactarrangement of claim
 4. 17. A circuit breaker including the vacuuminterrupter of claim
 13. 18. A circuit breaker including the vacuuminterrupter of claim
 14. 19. A circuit breaker including the vacuuminterrupter of claim
 15. 20. A circuit breaker including the vacuuminterrupter of claim 16.